title: Self-expandable metal stents and trans-stent light delivery: are metal stents and photodynamic therapy compatible?
abstract: OBJECTIVE
  Obstructive non-small cell lung cancer and obstructive esophageal cancer are US FDA approved indications of photodynamic therapy (PDT). The usefulness of PDT for the treatment of cholangiocarcinoma is currently under clinical investigation. Endoscopic stenting for lumen restoration is a common palliative intervention for those indications. It is important to assess whether self-expandable metal stents are compatible with trans-stent PDT light delivery.
  
  
  METHODS
  Direct effects of various components of metal biliary (n = 2), esophageal (n = 2), and bronchial (n = 1) stents on PDT light transmittance and distribution were examined using a point or linear light source (630 or 652 nm diode laser). Resected pig biliary duct and esophageal wall tissues were used to examine the feasibility of PDT light delivery through the fully expanded metal stents.
  
  
  RESULTS
  While using a point light source, the metal components (thread and joint) of the stent could cause a significant shadow effect. The liner material (polytetrafluoroethylene or polyurethane) could cause various degrees of light absorption. When the stent was covered with a thin layer of biliary duct and esophageal tissues containing all wall layers, the shadow effect could be mitigated due to tissue scattering.
  
  
  CONCLUSIONS
  This study clearly demonstrates that it is feasible to combine stenting and PDT for the treatment of luminal lesions. PDT light dose should be adjusted to counteract the reduction of light transmittance caused by the metal and liner materials of stent.
authors.affiliation: Department of Gastroenterology, Changhai Hospital, Shanghai, PR China.
authors.forename: Luo-Wei
authors.initials: LW
authors.lastname: Wang
authors.forename: Li-Bo
authors.initials: LB
authors.lastname: Li
authors.forename: Zhao-Shen
authors.initials: ZS
authors.lastname: Li
authors.forename: Yang K
authors.initials: YK
authors.lastname: Chen
authors.forename: Fred W
authors.initials: FW
authors.lastname: Hetzel
authors.forename: Zheng
authors.initials: Z
authors.lastname: Huang
mesh_terms: D000497:Alloys; D000818:Animals; D001652:Bile Ducts; D000075202:Contraindications; D004867:Equipment Design; D004947:Esophagus; D008422:Materials Testing; D055620:Optical Phenomena; D010778:Photochemotherapy; D011138:Polytetrafluoroethylene; D011140:Polyurethanes; D013193:Stainless Steel; D015607:Stents; D013552:Swine; D046509:Tissue Culture Techniques
chemical_list: D000497:Alloys; D011140:Polyurethanes; D013193:Stainless Steel; C013616:nitinol; D011138:Polytetrafluoroethylene